$2 \mathrm{~A}_{10}-\mathrm{A}_8=\left|\begin{array}{ccc}20 & 1 & \frac{\mathrm{n}^2}{2}+\alpha \\ 40 & 2 & \mathrm{n}^2-\beta \\ 56 & 3 & \frac{\mathrm{n}(3 \mathrm{n}-1)}{2}\end{array}\right|-\left|\begin{array}{ccc}8 & 1 & \frac{\mathrm{n}^2}{2}+\alpha \\ 16 & 2 & \mathrm{n}^2-\beta \\ 22 & 3 & \frac{\mathrm{n}(3 \mathrm{n}-1)}{2}\end{array}\right|$
$\Rightarrow\left|\begin{array}{ccc}12 & 1 & \frac{n^2}{2}+\alpha \\ 24 & 2 & n^2-\beta \\ 34 & 3 & \frac{n(3 n-1)}{2}\end{array}\right|$
$\Rightarrow\left|\begin{array}{ccc}0 & 1 & \frac{\mathrm{n}^2}{2}+\alpha \\ 0 & 2 & \mathrm{n}^2-\beta \\ -2 & 3 & \frac{\mathrm{n}(3 \mathrm{n}-1)}{2}\end{array}\right|$
$\Rightarrow-2\left(\left(\mathrm{n}^2-\beta\right)-\left(\mathrm{n}^2+2 \alpha\right)\right)$
$\Rightarrow-2(-\beta-2 \alpha) \Rightarrow 4 \alpha+2 \beta$